Automated manufacture of anisotropic electrospun scaffolds towards articular cartilage repair

Ângela Semitela (a) , Andreia Leal Pereira (a), Ana Capitão (b) , Alexandrina Mendes (b) , Paula A.A.P. Marques (a) and António Completo (a) (a) – TEMA, Department of Mechanical Engineering, University of Aveiro, Portugal (b) – CNC, Centre for Neuroscience and Cell Biology, University of Coimbra, Portugal (a) – Aveiro, Portugal; (b) – Coimbra, Portugal (a) – angela.semitela@ua.pt

Abstract — To date, cartilage tissue engineering (TE) strategies have had some success, developing replacement tissue constructs for articular cartilage. Yet, most of these tissueengineered constructs do not possess a native layered structure, particularly the collagen fibers alignment, progressing from parallel in the superficial zone, to random in the middle zone, and finally orientating perpendicular in the deep zone [1]. Given the nanofibrous topography of these collagen fibres, electrospinning has been widely employed for the development of fibrous scaffolds for cartilage TE [2]. Still, it remains a challenge to develop threedimensional (3D) electrospun scaffolds with a specific depthdependent fibrous alignment, as well as a uniform chondrocyte distribution. While some progress has been made in the development of these 3D anisotropic electrospun scaffolds by means of post-processing strategies of the electrospun meshes, several concerns still remain, particularly the design reproducibility and the ineffective chondrocyte infiltration [3].

So, in this work, we attempt to fabricate chondrocyte-laden 3D anisotropic electrospun scaffolds in a totally automated manner using a newly developed electromechanically 3D electrospinning platform [4], in order to develop functional articular cartilage tissue constructs.

A polymeric blend of polycaprolactone (PCL) and Gelatin (GEL) was employed, and the PCL+GEL fibres were collected and placed in a collector to adjust fibre alignment. An immortalized human chondrocyte cell line C28/I2 was pipetted between the fibrous layers. Chondrocyte-laden scaffolds were cultured under static and perfused conditions for 21 days. The 3D scaffolds and the respective cell-seeded constructs were characterized based on their topographic, mechanical and biological properties.

The 3D scaffolds were successfully fabricated with a slight arcade-like fibrous arrangement, while maintaining a high level of porosity. This was particularly important for an effective nutrient delivery and waste removal during culture, even under static conditions, where this is only performed via molecules diffusion. Moreover, the 3D scaffolds possessed an enhanced water absorption capacity, related not only with the elevated porosity, but also with the presence of the hydrophilic GEL, translating in a nearly total deformation recovery after compression at 20%. The in vitro results demonstrated that, even though a substantially low percentage of viable chondrocytes was observed after 1 day of culture, the remaining chondrocytes were able to proliferate over time. Additionally, under perfused conditions, the percentage of viable cells was significantly higher, suggesting its beneficial impact of chondrocyte metabolism. The compression modulus of the 3D scaffolds fell in the range of values reported for native articular cartilage, and it was significantly increased upon culture under perfused conditions, suggesting that flow perfusion enhanced chondrocyte synthesis of extracellular matrix elements, which translated in an increased biomechanical strength of the chondrocyte-laden 3D scaffolds.

Keywords — Cartilage tissue engineering, 3D electrospun scaffolds, Anisotropic, Chondrocyte-laden.

ACKNOWLEGEMENTS

This work was supported by the Portuguese funding of Program COMPETE-FEDER, Programa Operacional Competitividade e Internacionalização through the projects POCI-01-0145-FEDER-028424 and CENTRO-01-0145FEDER-022083. Also, by Fundação para a Ciência e Tecnologia I.P. (FCT, IP) through the projects PTDC/EMESIS/28424/2017, UIDB/00481/2020 and UIDP/00481/2020. The authors thank to FCT for the PhD grant SFRH/BD/133129/2017.

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REFERENCES

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[4] Completo, A., Marques P, J. 2020 – “Electrospinning system and process for large-scale manufacturing of aligned 3D fiber matrices”. European Patent Office (EPO) - EP3670714 (A1).